Telephone receiver



June 23, 1925. 1,542,922

G. K. THOMPSON TELEPHONE RECEIVER Filed April 2;. 1923 IN VE N TOR mORA/E Y Patented June 23, 1925 UNITED STATES PATENT. OFFICE.

' GEORGE K. THOMPSON, OF MAPLEWOOD, 1T ERSEY, ASSIGNOR AMERICAN TELE- PHONEA ND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK- TELEPHONE nncmvnn.

To all whom it mag 0012mm:

' the pole pieces re Be it known that I, Gnonc'n K. THOMPSON, residing at Maplewood, in the county of Essex and State of New J ersey, have invented certain Improvements in Telephone Receivers, of which .the following is a specificat-ion.

Thisinvention relates to telephone receivers, and more particularly to electromagnetic telephone receivers including permanent magnets. p

In the development of electromagneticreceivers, difficult is found on long lines with the current at its minimum in securing the desired steady magnetic flux. One method of producing theadditional flux desired is to use a permanent magnet. To such an arrangement, however, there is this objection: In order that the best results may be obtained, the receiver must be properly poled; and, if the current flow through the Windings happens to be such as to neutralize the effect of the permanent magnet, there is a serious loss in efficiency. -Furthermore, in common battery circuits it is not desirable to use a receiver. which requires oling, as there are many points at which t e circuit may be transposed,lwith. the result. of an improper polin of the receiver.. Applicants invention'aims to solve the problem outlined above,.and has as its rincipal object the production of a telep one receiver whichwill have a uniform magnetic flux through the pole pieces regardless of the direction of the energizing current.

The arrangement includes the usual electromagnets with coils wound in opposite directions and connected in series and a diaphragm adjacent to the upper poles. A U- shaped permanent magnet carries polepieces attached by means of flexible strips and free tomove laterally; and the lower ends of the electromagnet cores and these pole pieces are so arranged that upon the energizing of the electromagnets one pole piece is attracted to each core, whatever the direction of the current in the electromagnet windings, thus maintaining a steady magnetic flux through ardless of the direction of the current in t e windings.-

The following is a detailed description of one desirable embodiment of the invention. This description is to be read with reference to the accompanyin which the single figure shows in perspective polarity,

tively drawing, in

Serial No. 633,754.

one construction and arrangement of the'essenti'al parts of the receiver according to ap licants invention.

ith reference to the details of the drawing, 1 designates the diaphragm, partially cut away to expose the parts below. '2 and 3 are two-L-shaped soft iron cores, the upper ends of which are placed adjacent to the central section of thediaph'ragm, according to the practice well established in the art; 4 and 5 designate the core windings, which are wound inopposite directions and con' nected in series-the usual arrangement .in bi-polar receivers. The lower extremities ofthe cores 2vand 3 are placed adjacent to two movable soft iron tongues 6 and 7. These tongues are given each a permanent polarity by means of a U-shaped permanent magnet, whose twoarmsare shown as 8 and 9. In each arm of'the permanent magnet there a deep slot, as clearlyjshown in the drawing. The tongue 6 is mountedin the slot of the magnet arm 8 by means of a thin and flexible soft iron strip 10, being free to movefrom one side of the slot to the other. The tongue 7 is in a like manner movably mounted in the slot of the magnet arm 9.

The pole marking in the drawing will lead of the operation of to a clear understanding is now descr bed the receiver parts, which as follows:

Suppose the end of the arm 8 to be the north seeking poleof the permanent magnet and the end of the arm 9 to be the south pole. It is obvious that the movable tongues 6 and 7, mounted as described above, will act as pole pieces, havin' a north and a south respectively. ow, suppose a curthrough the core windings to make the upper end of the core 2 a north pole. The lower end of the core 2 will, of course, have a south polarity, and the upper and lower poles of the core 3 will besouth and north, respecappears clearly from a consideration of the winding of the cores. The tongue 6, which constitutes the north seeking pole piece of the permanent magnet, will be attracted to the lower end of the core 2, which has a south polarity, and likewisethe tongue 7 which constitutes the south pole piece of the permanent magnet, will be attracted to the lower end of the core 3, which is shown to have a north polarity. The

rent to be passed in such a direction as drawing shows the parts oi the receiver in this position. Should the current in the ity of the cores 2 and 3 would be the opposite of that shown in the drawing. As a result, the pole pieces 6 and 7 would move, 6 being attracted to the core 3 and 7 being attracted to the core '2. Thus, the reversal of the current in the receiver windings has no effect on the amount of the magnetlc flux through the pole pieces-but merely reverses the direction of the flux.

What is claimed is: 4

1. A telephone receiver comprising a permanent magnet, two electromagnets presenting upper ends of opposite polarity to a diaphragm, the lower ends of sald electromagnets lying above said permanent magnet, and two pole pieces movably mounted on said permanent extending between the lower ends of the electromagnets, each pole piece being free to respond to attraction-toward either electromagnet. v

2. A telephone receiver comprising Y a U-shaped permanent magnet, two electromagnets presenting upper ends of opposite polarity to a diaphragm, the lower ends of said electromagnets lying above said permanent magnet, and two pole pieces movably mounted on said permanent magnet, said pole piecesextending between the lower ends of the electromagnets, each pole piece being free to respond to attraction toward either electromagnet.

3. In a telephone receiver, in combination, a U-shaped permanent magnet, two electromagnets presenting upper ends of op posite polarity to a diaphragm, the lower ends of said electromagnets' lying above said permanent magnet, and two pole pieces movably mounted on said permanent magnet, said pole pieces extending between the lower ends of the electromagnets, each pole piece being free to respond to attraction toward either electromagnet.

4. In a telephone receiver, in combination, two electromagnets including coils wound in opposite directions and connected in windings be reversed in direction, the polarl ,electromagnets, a U-shape magnet, said pole pieces series, the upper poles of said electromagnets lying adjacent to a diaphragm and the ower poles facing each other; and a U-shaped permanent magnet, said magmt carrying pole pieces movably mounted thereon, said pole pieces extending between the-lower poles of the electromagnets, being free to move laterally between said poles.

5. In a telephone receiver, in combination, two electromagnets comprising L- shaped cores and coils wound in opposite directions and connected in series, a diaphragm adjacent to theup r poles of said permanent magnet, and pole pieces connected to said magnet by flexible strips, said pole pieces extending between the lower ends of the L-shaped electromagnet cores, being free to move laterally between the same. r

6. .In a telephone receiver including two electromagnets comprising cores and coils wound in opposite directions and connected in series, a diaphragm adjacent to the upper ends of manent magnet; as means for a steady magnetic flux in the pole pieces movably mounted manent magnet and extended between the lower ends of the electromagnet cores, said pole pieces being free to respond to attracmaintaining receiver, two on said pertion toward either of said cores.

7. In a telephone receiver including two eleotromagnets comprising cores and coils wound in opposite directions and connected in ser es, a diaphragm adjacent to the upper ends of said cores, and a U-shaped permanent magnet; as means for maintaining a steady magnetic flux in the receiver, two pole pieces mounted on said ermanent magnet by flexible strips, said pole pieces extending between the lower ends of the electromagnet cores, each pole piece being free to respond to attraction toward either of said cores.

In testimony whereof, I have signed in name to this specification this 20th day of April, 1923.

GEORGE K. THOMPSON.

said cores, and a U-shaped per- 

